Add the JNI code in order to let Java use the InterestsFetcher.

chrome/browser/interests/android/interests_service.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/interests/android/interests_service.h"
+
+#include "base/android/jni_android.h"
+#include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
+#include "base/android/scoped_java_ref.h"
+#include "chrome/browser/interests/interests_fetcher.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/browser/profiles/profile_android.h"
+#include "jni/InterestsService_jni.h"
+
+using base::android::AttachCurrentThread;
+using base::android::ConvertJavaStringToUTF8;

[Bernhard Bauer, 2015/10/08 09:04:41]

This is unused.

[PEConn, 2015/10/08 09:40:55]

Done.

+using base::android::ConvertUTF8ToJavaString;
+using base::android::ScopedJavaGlobalRef;
+using base::android::ScopedJavaLocalRef;
+using base::android::ToJavaArrayOfStrings;

[Bernhard Bauer, 2015/10/08 09:04:41]

This is unused.

[PEConn, 2015/10/08 09:40:55]

Done.

+
+InterestsService::InterestsService(Profile* profile)
+    : profile_(profile), weak_ptr_factory_(this) {}
+
+InterestsService::~InterestsService() {}
+
+void InterestsService::Destroy(JNIEnv* env, jobject obj) {
+  delete this;
+}
+
+void InterestsService::GetInterests(JNIEnv* env,
+                                    jobject obj,
+                                    jobject j_callback_obj) {
+

[Marc Treib, 2015/10/08 08:26:51]

nit: no empty line here

[PEConn, 2015/10/08 09:40:55]

Done.

+  ScopedJavaGlobalRef<jobject> j_callback(env, j_callback_obj);
+
+  scoped_ptr<InterestsFetcher> fetcher =
+      InterestsFetcher::CreateFromProfile(profile_);
+  InterestsFetcher* fetcherRawPtr = fetcher.get();

[Bernhard Bauer, 2015/10/08 09:04:41]

Nit: |fetcher_raw_ptr|. I know, mixing Java and C++ style is confusing ☺

[PEConn, 2015/10/08 09:40:55]

Done.

+
+  InterestsFetcher::InterestsCallback callback = base::Bind(
+      &InterestsService::OnObtainedInterests,
+      weak_ptr_factory_.GetWeakPtr(),
+      base::Passed(fetcher.Pass()),
+      j_callback);
+
+  fetcherRawPtr->FetchInterests(callback);
+}
+
+// static
+bool InterestsService::Register(JNIEnv* env) {
+  return RegisterNativesImpl(env);
+}
+
+jobjectArray InterestsService::ConvertInterestsToJava(

[Bernhard Bauer, 2015/10/08 09:04:41]

I think it would make sense to use a ScopedJavaLocalRef for the local variable
and return value, just to make we sure don't accidentally call into a Java
method in between, the JVM decides to do a garbage collection, and throws away
the object.

[PEConn, 2015/10/08 09:40:55]

Done.

+    JNIEnv* env,
+    scoped_ptr<std::vector<InterestsFetcher::Interest>> interests) {
+  if (!interests)
+    return nullptr;
+
+  jobjectArray j_interests =
+      Java_InterestsService_createInterestsArray(env, interests->size()).obj();
+
+  for (size_t i = 0; i != interests->size(); i++) {
+    InterestsFetcher::Interest& interest = (*interests)[i];

[Bernhard Bauer, 2015/10/08 09:04:41]

Make this const?

[PEConn, 2015/10/08 09:40:55]

Done.

+    ScopedJavaLocalRef<jobject> j_interest =
+        Java_InterestsService_createInterest(
+            env,
+            ConvertUTF8ToJavaString(env, interest.name).obj(),
+            ConvertUTF8ToJavaString(env, interest.image_url.spec()).obj(),
+            interest.relevance);
+
+    env->SetObjectArrayElement(j_interests, i, j_interest.obj());
+  }
+
+  return j_interests;
+}
+
+void InterestsService::OnObtainedInterests(
+    scoped_ptr<InterestsFetcher> fetcher,
+    const ScopedJavaGlobalRef<jobject>& j_callback,
+    scoped_ptr<std::vector<InterestsFetcher::Interest>> interests) {
+  JNIEnv* env = AttachCurrentThread();
+  jobjectArray j_interests = ConvertInterestsToJava(env, interests.Pass());
+  Java_GetInterestsCallback_onInterestsAvailableCallback(env,
+                                                         j_callback.obj(),
+                                                         j_interests);
+}
+
+static jlong Init(JNIEnv* env,
+                  const JavaParamRef<jobject>& jobj,
+                  const JavaParamRef<jobject>& jprofile) {
+  InterestsService* interests_service =
+      new InterestsService(ProfileAndroid::FromProfileAndroid(jprofile));
+  return reinterpret_cast<intptr_t>(interests_service);
+}